Dam Safety: DCR completes storm analyses

December 18, 2015

Pursuant to companion measures HB1006 (Byron) and SB582 (Garrett), the Department of Conservation and Recreation (DCR) was directed by the 2014 General Assembly to study a storm-based approach to calculate “Probably Maximum Precipitation” (PMP) for all different regions of Virginia. The purpose of the study was to determine whether costs associated with repair and upgrade of older dams (many of which are owned by local governments) may be excessive when considering the severity of storms that are more likely to be experienced in Virginia in the future.

A chief criticism of current standards relating to dam safety is that they are based on assumptions of much more severe storms that, on a statistical basis, are considered “probable.” DCR’s study was based upon a review of storm records dating back to the early 1800s. Under HB 1006/SB 582 the deadline for DCR to complete its study was December 2015.

On December 10, DCR’s staff presented its findings to the Soil and Water Conservation Board, and estimated that the costs of upgrading and repairing dams currently in need of rehabilitation could be reduced by about $72 million if newer “PMP” standards were to be adopted and incorporated within Virginia’s regulations. According to DCR this is a conservative estimate.

Much of DCR’s report is highly technical, and provides much detail about the effects of storm events on different areas of the state, with additional information about topographical and hydrological factors. DCR’s study entailed a review of storm events in Virginia going back to the early 1800s.

In response to DCR’s report, the Soil and Water Conservation Board proposed amendments to its regulations relating dam safety. But before the new rule undergoes public comment under Administrative Process Act (APA) procedures it will receive a review by the Department of Planning and Budget. Because of the strong interest many of its members have in costs associated with the repair and upgrade of aging dams, the General Assembly is also likely to review the PMP study during the 2016 session.